Removal of the sialoliths surgically, either through the mouth or through the outside skin, is the treatment of choice, provided the stone is accessible.
Saliva glands can become infected and inflamed and this is referred to as sialodenitis. Clinically, the affected gland is warm and painful to palpate and can cause difficulty with eating and swallowing. Infection is usually secondary to other issues with the gland or duct such as sialoliths, trauma, dental disease, or rupture of the duct. Treatment is based on removing/treating the initial cause of the infection and using antibiotics that have been selected based on culturing the offending bacteria.
Salivary glands and ducts can be damaged from traumatic incidents such as blunt force trauma or lacerations, and these can cause a partial or complete reduction in the flow of saliva through the duct due to swelling, which will continue until the swelling subsides. In cases where the duct has been transected (cut in two), the outcome will depend on whether the two ends of the duct can be joined either surgically or if they reattach when healing.
With wounds that originate on the outside of the body and extend down through the tissues into or straight through the duct, saliva can be observed to drip from the wound as the horse eats. When the gland itself is damaged, they may be some saliva seen dripping, but this is not as profuse as that seen when the duct is involved. The duct will usually heal with time, although in some cases, surgery to repair or relocate the duct can be performed. In cases where the saliva continues to leak out through the skin, chemical ablation or surgical removal of the parotid duct can be performed to stop the fluid and electrolyte loss that occurs with continuous saliva flow.
Tumors in the salivary glands are rare, with the most common form being a melanoma in grey horses. Occasionally tumors will invade the gland from an adjacent location, necessitating the removal of the gland if surgery is viable (based on the type of tumor and where it originates).
Other rare conditions include atresia of the parotid duct which is a failure of the duct to develop properly, causing a blockage somewhere between the gland and the mouth, and the failure of saliva to flow. The duct will dilate and rupture if an opening into the mouth cannot be constructed surgically or the gland removed or ablated to eliminate saliva production.
Excessive salivation can be seen in some horses, but this is often a symptom of an underlying problem and not a primary illness of the salivary glands. Injury or damage to the mouth such as a lacerated tongue or dental disease can result in excess saliva in the mouth due to the horse failing to swallow and allowing saliva to accumulate in the mouth.
Similarly, any nerve paralysis in the pharynx causing a dysphagia will see saliva and feed dropped from the mouth. Some medications or chemicals given orally can burn the mouth causing increased salivation and there are plant toxins that stimulate the salivary gland to produce saliva. Therefore, a thorough history should be sourced on any horse found to be salivating abnormally as well as it undergoing a thorough oral examination, including an endoscopic examination of the pharynx if nothing is detected in the oral cavity. Any prolonged loss of saliva can be detrimental to the horse as it can cause dehydration and electrolyte losses. EQ